In the production of polyolefins, such as for example polyethylene, an important aspect of the various processes and catalysts used to produce such polymers is the productivity. By productivity is meant the amount of solid polymer that is obtained by employing a given quantity of catalyst. If the productivity is high enough, then the amount of catalyst residues contained in the polymer is low enough that the presence of the catalyst residues does not significantly affect the properties of the polymer, and the polymer does not require additional processing to remove the catalyst residues. As those skilled in the art are aware, removal of catalyst residues from polymer is an expensive process. It is thus desirable to employ a catalyst which provides sufficient productivity that catalyst residue removal is not necessary.
Another important aspect in the production of polyolefins, is the rate of incorporation of comonomer during polymerization. A low rate of comonomer incorporation requires the presence of higher concentrations of comonomer during polymerization to produce a polymer having the desired density. Unreacted comonomer residue causes odor problems in the polymer and higher production costs. Increasing the rate of comonomer incorporation would allow a lower comonomer concentration during polymerization, which would mean a lower cost in reactants and in comonomer removal and/or recycling.
It would therefore be desirable to produce a catalyst system which provides sufficient productivity that catalyst residue removal is not necessary. It would also be desirable to prepare a catalyst system that is capable of incorporating comonomer at efficient levels.